1. Field of the Invention
This invention relates to a multichannel catheter, i.e. a perfusion cannula, useful in arterial perfusion of the aorta, generally via a femoral artery for use in conjunction with cardiovascular examinations, treatments and surgery. It also relates to methods for making and using such a catheter.
2. Background of the Invention
To better understand the background and problems faced by those of skill in this area of technology it is useful to understand the basic workings of the heart and circulatory system. The following discussion refers to schematics of the heart shown in FIGS. 1 and 2. The human heart is a muscular pump having four separate cavities and a series of valves allowing blood to pass in one direction only. Mammals, including humans, have a double circulatory system. Blood that has released oxygen to the tissues 9 and 14 and has absorbed carbon dioxide from them (venous blood) is returned to the heart through the superior and the inferior venae cavae 11 and 10. This blood enters the right auricle 3, whose contractions cause the blood to pass through the tricuspid valve 16 in the right ventricle 1. The contractions of the right ventricle pass the blood through the pulmonary semilunar valves 17 and along the two pulmonary arteries 5 into the lungs 6. In the lungs, the blood is oxygenated and returns to the heart through the pulmonary veins 7 and thus enters the left auricle 4. This chamber contracts and passes the blood through the bicuspid, or mitral, valve 15 into the left ventricle 2, whose contractions force the blood through the aortic semilunar valve 18 into the aorta 12 and 13, which is the biggest artery of the body and to other parts of the body through, i.a., the great arteries 8. Thus the right side of the heart serves mainly to pump deoxygenated blood through the lungs, while the left side pumps oxygenated blood throughout the rest of the body. This is represented as a flow schematic in FIG. 2, where similar numbers refer to similar parts of the heart. The heart varies the output by varying the volume of blood admitted into the ventricles each time the latter are filled and also by varying the rate of contraction (faster or slower heartbeat). The left side of the heart (left auricle and ventricle) has to circulate the blood through all parts of the body, except the lungs, and has thicker and more strongly muscular walls than the right side, which has to perform the pulmonary blood circulation only. For proper functioning, the left side and the right side must be accurately interadjusted, both with regard to the contraction rate of the respective chambers and with regard to the output of blood. When functional disorders of the heart occur, it may be necessary to examine the heart to determine the problem and possibly perform surgery or provide treatment.
In performing examinations or treatments of a subjects heart, or performing surgery on the hear; it is often necessary to reduce the rate at which it normally beats or stop its beating completely. This allows a physician to observe, or operate on, the heart more easily. However, by reducing or stopping the heart rate (i.e. cardioplegia), blood will not be adequately circulated to the rest of the body. Thus, it is generally necessary to circulate the blood using some type of extracorporeal blood circulating means that regularly circulates oxygen-rich blood through the arteries, collects oxygen-depleted blood returning through the veins, enriches the oxygen-depleted blood with additional oxygen, then again circulates the oxygen-rich blood.
The types of examinations, treatments and operations that require some degree of cardioplegia or drug delivery and extracorporeal blood circulation include open heart surgery and less-invasive heart surgery to perform single or multiple coronary artery bypass operations, correct malfunctioning valves, etc. Others include, but are not limited to, myocardial revascularization, balloon angioplasty, correction of congenital defects, surgery of the thoracic aorta and great vessels, and neurosurgical procedures.
The extracorporeal blood circulation generally requires the use of some type of heart-lung machine, i.e. a cardiopulmonary machine. This has the threefold function of keeping the replacement blood in circulation by means of a pumping system, of enriching with fresh oxygen the blood of low oxygen content coming from the patient's body, and regulation of patient temperature. The system shown in FIG. 3 diagrammatically describes the manner in which such a machine works.
The venous blood, before it enters the right auricle of the heart is diverted into plastic tubes 20, generally by gravity flow. The tubes are positioned to receive the blood from the superior and inferior venae cavae (shown as 11 and 10 in FIG. 1). This blood, which has circulated through the body and consequently has a low oxygen content is collected in a reservoir 21. A blood pump 22 is used to pump the blood through a heat exchanger 23 and artificial lung 24. The heat exchanger 23 and artificial lung 24 may be one of several designs to regulate blood temperature and increase the oxygen content of the blood. Modern designs use advanced membrane technology to achieve the oxygenation, which is similar to the way red blood cells absorb oxygen from the human lung. The oxygenated blood then passes through a filter 25 and is returned to the patient. Losses of blood occurring during the course of the operation are compensated by an additional blood reservoir 26. Collected blood is passed through a defoamer 27 and is likewise passed to the reservoir 21, heat exchanger 23 and artificial lung 24. Before starting the cardiopulmonary bypass machine the extracorporeal circuit is filled with one or two liters of saline solution. In circulating the oxygenated blood to the body from filter 25, it can be pumped through a catheter 28 by inserting the catheter into the aorta or one of its major branches and pumping the blood through the catheter. However, when the heart is to be operated on, it must be free of blood and sometimes the heart beat must be reduced or stopped completely. Referring again to FIG. 1, blood is prevented from entering the heart by blocking the ascending aorta 12 near the semilunar valve 18 while at the same time preventing blood from entering the right auricle 3 by withdrawing blood through the superior vena cavae 11 and inferior vena cavae 10. Blocking the ascending aorta may be achieved by clamping or preferably by balloon blockage. At the same time that blood is prevented from flowing through the heart, a cardioplegia solution is administered locally to the heart to arrest the heart. Thus, there is a need for a device that allows a heart specialist to locally administer cardioplegia to the heart, block the flow of blood to the heart, while at the same time circulating oxygenated blood to the patient's body, particularly through the great arteries 8 in FIG. 1, to ensure all limbs and tissues remain undamaged during the heart examination or operation. Several devices are described in the literature to address the need for an appropriate device. One example is disclosed in U.S. Pat. No. 5,312,344 issued 17 May 1994 to Grinfeld et al.
Another example can be seen in U.S. Pat. No. 5,433,700, issued 18 Jul. 1995 to Peters. This patent describes a process for inducing cardioplegic aeest of a heart which comprises maintaining the patient's systemic circulation by peripheral cardiopulmonary bypass, occluding the ascending aorta through a percutaneously placed arterial balloon catheter, venting the left side of the heart, and introducing a cardioplegia agent into the coronary circulation. As part of the disclosure a multichannel catheter is disclosed which provides channels for the cardioplegia solution, a fluid transportation to inflate the balloon, a lumina for instrumentation and a separate catheter to deliver oxygenated blood to the body.
Another example of a device is found in U.S. Pat. No. 5,478,309, issued 26 Dec. 1995 to Sweezer et al. This is a rather complex device and system of venous perfusion and arterial perfusion catheters for use in obtaining total cardiopulmonary bypass support and isolation of the heart during the performance of heart surgery.
Another device is described in U.S. Pat. No. 5,458,574, issued 17 Oct. 1995 to Machold et al. It shows a multichannel catheter which has channels for fluid to blow up balloons for blocking the aorta, a channel for cardioplegia solution and a channel for instruments for examining the heart.
Still another patent, U.S. Pat. No. 5,452,733, issued 26 Sep. 1995 to Sterman et al.
Another patent application, PCT/US 94/09938, having international publication number WO095/08364, filed 1 Sep. 1994 in the name of Evard et al., describes an endovascular system for arresting the heart. PCT International Application number PCT/US 94/12986, published as Publication number WO95/15192, filed 10 Nov. 1994, in the name of Stevens et al., provides a description of a partitioning device that is coupled to an arterial bypass cannula. U.S. Pat. No. 5,868,703, issued 9 Feb. 1999 (the '703 patent), discloses an improved device that aids a surgeon in performing open or closed heart surgery.
However, the design of the improved device has led to certain problems in the smooth operation of the device. For example, the design of the '703 device requires the presence of blood outlets strategically located along a portion of the multichannel catheter. When the distal tip of the device, which carries the balloon, is inserted into a femoral artery through a percutaneous opening, some of the blood portal will be located inside the artery (interior portals) while others will be temporarily located outside the artery (exterior portals). For a short period of time, blood, which flows in the artery will enter the catheter through the interior blood portal then exit through the exterior portals. This problem is solved by this invention through using an internal, slidable obturator in the blood flow channel to block both the interior & exterior portals during insertion of the multichannel catheter until all the portals are located within the artery. The obturator is then withdrawn to allow blood from a cardiopulmonary machine to be pumped through the blood flow channel of the multichannel catheter.